JPH11111265A - Polymer electrolyte secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce internal resistance of a battery, attain size reduction, increase capacity, and improve a rapid charge/discharge characteristic and charge/discharge cycle durability by forming a positive electrode body and/or a negative electrode body of a foaming metallic plate which does not form an allay with lithium or a metallic fiber sintered plate, and filling an electrode layer inside a metallic current collecting body. SOLUTION: A positive electrode body and/or a negative electrode body are integrally formed in a condition where a current collecting body three-dimensionally expands in a mixture by filling the mixture containing an active material and a polymer electrolyte in the current collecting body composed of a foaming metallic plate which does not form an alloy with lithium or a metallic fiber sintered plate. Therefore, an average distance between the active material and the current collecting body is small, and internal resistance of an electrode body is small. Therefore, a battery having large capacity is obtained, and can endure even large electric current discharge. In the electrode body, the active material is fixed by a polymer electrolyte also having a function as a binder together with the foaming metallic plate, and even if charge/ discharge is repeated, an increase in internal resistance of the electrode body can be restrained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a secondary battery using a polymer electrolyte, and more particularly to a polymer electrolyte secondary battery having a large capacity, a small internal resistance and an excellent cycle life.

[0002]

2. Description of the Related Art A battery using a material capable of occluding and releasing an alkali metal or an alkali metal ion as an electrode active material has attracted attention as having a high energy density. Among them, a lithium secondary battery has a particularly high energy density. For,
It is being widely used as a power source for electronic devices.

[0003] When a liquid electrolyte is used for the primary battery and the secondary battery, measures have been devised to reduce leakage and the ignitability of the flammable electrolyte. In recent years, polymer electrolytes have been proposed from the viewpoints of measures against these problems, improvement of incorporation into electronic devices by forming batteries into a film, and effective use of space (Japanese Patent Application Laid-Open No. Hei 8-50740).
7, Tokuhyo Hei 4-506726).

Among them, polyethylene oxide-based polymer electrolytes are electrochemically stable, but have a drawback in that the solvent retention of the organic electrolyte is low. The polyacrylate-based polymer electrolyte having a three-dimensional structure has good solvent retention, but is electrochemically unstable and is not suitable for a high-potential battery.

[0005] A polymer electrolyte made of polyvinylidene fluoride is electrochemically stable and has a feature that the polymer has high heat resistance because it contains fluorine atoms. However, when the temperature of the polymer electrolyte is increased, the electrolyte oozes out of the polymer. On the other hand, there is an attempt to solve this problem by using a copolymer of vinylidene fluoride and hexafluoropropylene.

In a conventional polymer electrolyte secondary battery, for example, a slurry composed of a positive electrode active material or a negative electrode active material and a polymer electrolyte is applied to the surface of a current collector metal foil to form a 50-100 μm slurry.
An electrode layer having a thickness of m is formed and dried to form a positive electrode body and a negative electrode body, and between the positive electrode body and the negative electrode body, a device in which a polymer electrolyte film is interposed as a separator or a basic device,
Alternatively, a multi-layer element is formed by alternately stacking a large number of sheets with a separator film between a sheet-like positive electrode body and a negative electrode body,
This element was sealed with an exterior laminate film to form a battery.

[0007]

In order to increase the capacity per unit volume of the above-mentioned polymer electrolyte battery,
It is necessary to increase the content of the positive electrode active material in the positive electrode body and the content of the negative electrode active material in the negative electrode body. However, if the amount of the active material is increased, the amount of the polymer that functions as a binder in addition to the function of holding the non-aqueous electrolyte is relatively reduced, so that the adhesion to the current collector is reduced. Therefore, there has been a problem that peeling occurs between the electrode layer and the current collector foil after the charge / discharge cycle during the manufacturing process of the polymer electrolyte battery, the handling of the battery, and the battery performance is deteriorated.

[0008] When the electrode layer is thickened to increase the volume of the electrode layer per unit area, the electrode layer is more easily peeled from the current collector foil, and the electrical resistance in the thickness direction of the electrode, that is, the internal resistance is reduced. Because of the large size and long diffusion distance of lithium ions, the utilization rate of the electrode material is extremely low, and there is a problem that the energy density and the capacity are reduced accordingly. Particularly, the polymer electrolyte has a lower electric conductivity than the liquid electrolyte. Is remarkable.

It has been proposed to use a 10-30 μm thick aluminum foil having a roughened surface as a positive electrode current collector of a polymer electrolyte battery to form a 100 μm thick sheet-like positive electrode (Japanese Patent Laid-Open No. 9-22699). However, such a surface-roughened aluminum foil current collector has a partial effect in improving the adhesiveness. However, when the electrode layer is made to have a thickness of, for example, 150 μm or more, the electrode layer peels off, the internal resistance of the battery increases, and the capacity appears. There is a problem that it becomes difficult.

As described above, the conventional lithium secondary battery using a polymer electrolyte has a disadvantage that the internal resistance is high, large current discharge is difficult, the capacity is small, and the charge / discharge cycle durability is inferior to the battery using the liquid electrolyte. was there.

The present invention provides a polymer electrolyte secondary battery which employs a specific current collector to reduce the internal resistance of the battery, and has a small size, a large capacity, excellent rapid charge / discharge characteristics, and excellent charge / discharge cycle durability. provide.

[0012]

According to the present invention, there is provided a positive electrode and a negative electrode comprising a metal current collector and an electrode layer containing a non-aqueous solution containing an active material and an electrolyte and a polymer holding the solution. Body, a polymer electrolyte secondary battery having a polymer electrolyte interposed between the cathode body and the anode body and holding a non-aqueous solution containing an electrolyte,
The positive electrode body and / or the negative electrode body is a foamed metal plate or a metal fiber sintered plate made of a metal in which the metal current collector does not form an alloy with lithium, and the electrode layer is filled in the metal current collector. The invention provides a polymer electrolyte secondary battery characterized in that:

In this specification, a foamed metal plate or a sintered metal fiber plate that does not form an alloy with lithium refers to a foamed metal plate or a sintered metal fiber plate that does not form an alloy with lithium even after repeated charge / discharge cycles. . In addition, a positive electrode body in which a positive electrode layer made of a positive electrode active material, a polymer electrolyte, and a conductive material added as necessary is filled in the current collector and integrated with the current collector. The same definition applies to the negative electrode body.

The positive electrode body and / or the negative electrode body of the present invention (hereinafter, referred to as the “body”)
(Collectively referred to as an electrode body) is formed by filling a current collector made of a foamed metal plate or a metal fiber sintered plate that does not form an alloy with lithium with a mixture containing an active material and a polymer electrolyte. It is integrated in the mixture in a three-dimensionally spread state. Therefore, the average distance between the active material and the current collector is small, and the internal resistance of the electrode body is small. Therefore, a battery having a large capacity can be obtained and can withstand a large current discharge. In the electrode body, the mixture of the active material and the polymer electrolyte does not need to be completely filled in the pores of the current collector, but a smaller porosity of the electrode body is preferable because the capacity per volume can be increased. The porosity of the electrode body is 10%
The following is preferred.

The electrode body according to the present invention is obtained, for example, as follows. First, a polymer forming a matrix of a polymer electrolyte is dissolved or uniformly dispersed in an organic solvent, and mixed with a solution in which the electrolyte is dissolved in a non-aqueous solvent (hereinafter, this mixed solution is referred to as a mixed solution for forming a polymer electrolyte). This mixture and the active material powder are mixed to form a slurry,
This slurry is applied to a foamed metal plate or a sintered metal fiber plate and then dried to obtain a slurry. Preferably, it is then compressed by a press or the like.
When compressed, the porosity of the electrode body decreases, and the capacity per volume can be increased.

As the organic solvent for dissolving or dispersing the polymer, tetrahydrofuran (hereinafter referred to as THF), methyl ethyl ketone, methyl isobutyl ketone,
Toluene, xylene, N-methylpyrrolidone, acetone, acetonitrile, dimethyl carbonate, ethyl acetate, butyl acetate and the like can be used, but in order to selectively remove this organic solvent by drying, the boiling point of THF, acetone or the like is 100 ° C or less. Volatile organic solvents are preferred.

In the electrode body, an active material is fixed by a foamed metal plate or a sintered metal fiber plate and a polymer electrolyte which also functions as a binder, and the active material repeats expansion and contraction by a charge / discharge cycle. Even if there is, the contact state between the particles of the active material is maintained, the increase in the internal resistance of the electrode body is suppressed, and the particles of the active material do not fall off from the electrode body due to the charge / discharge cycle, and the initial capacity of the battery is reduced. Can be held.

The thickness of the electrode body in which the metal current collector and the electrode layer are integrated is preferably 0.2 to 2 mm. When the thickness is less than 0.2 mm, the amount of the active material carried is small and the battery capacity is small. On the other hand, if it is too thick, the resistance of the electrode body becomes large, and the practicality is poor. In particular, 0.3 to 1 mm is preferable in terms of battery characteristics.

As the metal current collector for the negative electrode, a foamed metal plate containing nickel as a main component, a sintered fiber plate containing nickel as a main component, or a sintered stainless steel plate is preferable. A metal containing nickel as a main component is not easily alloyed with lithium and has good conductivity. In addition, commercially available nickel foam metal sheets and nickel or stainless steel fiber sintered bodies are easily available. As stainless steel, ordinary inexpensive SUS30
4, SUS316, SUS316L, etc. can be used. Further, a copper foam metal plate or a copper fiber sintered metal can also be used.

The foamed metal plate used as the current collector for the negative electrode is preferably a spongy porous body having continuous cells. The opening diameter of the unit bubble of this bubble is 10 μm to 1.
It is preferably 0 mm. If the opening diameter is less than 10 μm, it becomes difficult to fill the mixture of the negative electrode active material and the polymer electrolyte into the air bubbles, and if it exceeds 1.0 mm, the average distance between the foamed metal plate as the current collector and the negative electrode active material is reduced. And the internal resistance of the electrode increases. From the viewpoint of ease of filling and internal resistance, the opening diameter is more preferably 30 to 500 μm.

The porosity of the foamed metal sheet is 70 to 98%.
It is preferred that If the porosity is less than 70%, the amount of the negative electrode active material and the polymer electrolyte that can be filled in the bubbles decreases, and the capacity of the battery decreases. If the porosity exceeds 98%,
The strength of the foamed metal plate decreases, and the strength of the negative electrode body decreases.

The metal fiber sintered plate used as the negative electrode metal current collector preferably has a fiber diameter of 1 to 50 μm. If it is less than 1 μm, it becomes difficult to fill a mixture of a negative electrode active material and a polymer electrolyte into a sintered metal fiber plate,
If it exceeds μm, the average distance between the foamed metal plate serving as the current collector and the negative electrode active material increases, and the internal resistance of the electrode increases.
From the viewpoint of ease of filling and internal resistance, 5 to 25 μm is more preferable.

It is preferable to use a short fiber or long fiber sintered plate as the fiber metal sintered plate. Unsintered metal fibers have low strength, are difficult to maintain the shape of a plate or the like, and also have insufficient electrical connection between metal fibers, resulting in high electrical resistance. Must be sintered. The porosity of the metal fiber sintered plate is preferably from 70 to 95%. If it is less than 70%, the amount of the negative electrode active material and the polymer electrolyte that can be filled decreases, and the capacity of the battery decreases. If it exceeds 95%, the strength of the fiber sintered plate is reduced, and the strength of the negative electrode body is reduced.

The negative electrode active material in the present invention is a material capable of inserting and extracting lithium ions. The material forming the negative electrode active material is not particularly limited, for example, lithium metal,
Examples thereof include a lithium alloy, a carbon material, an oxide mainly containing a metal belonging to Groups 14 and 15 of the periodic table, a carbon compound, a silicon carbide compound, a silicon oxide compound, titanium sulfide, and a boron carbide compound. As carbon materials, those obtained by thermally decomposing organic substances under various pyrolysis conditions, artificial graphite, natural graphite, soil graphite,
Expanded graphite, flaky graphite and the like can be used. As the oxide, a compound mainly composed of tin oxide can be used.

Of the above carbon materials, particularly, mesophase spherical carbon or short mesophase carbon fiber is preferably used as the carbon material capable of inserting and extracting lithium of the negative electrode. When mesophase spherical carbon is used, it can be packed at a high density due to its spherical shape, and the capacity per unit volume increases. It is more preferable to use mesophase spherical carbon having a particle size of 50 μm or less, in which case a large battery capacity can be obtained. When the mesophase carbon short fibers are used, the electrolyte solution is efficiently supplied to the electrode material by removing the gaps between the short fibers, and the charge / discharge characteristics by a large current are improved. It is more preferable to use short mesophase carbon fibers having a length of 100 μm or less. In this case, it is easy to fill the pores of the current collector with the foamed metal. Also,
It is preferable to use a thermal decomposition product of a condensed polycyclic hydrocarbon compound such as char pitch or coke because a high capacity secondary battery can be obtained.

The above-mentioned negative electrode active material preferably has a particle diameter of 1 to 30 μm from the viewpoint of developing the strength of the electrode layer itself. If the particle size is less than 1 μm, it becomes bulky and difficult to handle,
If it exceeds 30 μm, the slurry for forming the negative electrode layer tends to be unstable or the battery capacity tends to decrease.

The current collector of the positive electrode is preferably a current collector that is stable in the operating potential range, does not dissolve or elute, and has excellent conductivity. Specifically, a foamed metal plate containing aluminum as a main component, a sintered aluminum fiber plate, a sintered titanium fiber plate, and a sintered stainless steel plate are preferable because these conditions are satisfied. Among them, a foamed metal plate containing aluminum as a main component, an aluminum fiber sintered plate, a fibrous SUS316 sintered plate and a fibrous SUS316L sintered plate are industrially manufactured and easily available.

The foamed metal plate containing aluminum as a main component is preferably a spongy porous body having communicating bubbles. Further, the pore diameter of the unit foam is preferably 50 μm to 1.0 mm. If it is less than 50 μm, it becomes difficult to fill a mixture of the cathode active material and the polymer electrolyte into the bubbles,
If it exceeds 1.0 mm, the average distance between the foamed metal plate, which is a three-dimensional current collector, and the positive electrode active material increases, and the internal resistance of the positive electrode body increases.

The porosity of the foamed metal plate mainly composed of aluminum used for the current collector for the positive electrode is preferably 70 to 98%. If the porosity is less than 70%, the amount of the mixture of the positive electrode active material and the polymer electrolyte filled in the bubbles is reduced, and the battery capacity is reduced. On the other hand, if it exceeds 98%, the strength of the foamed metal plate is low, the fixation force of the positive electrode active material is reduced, and the expansion and contraction of the positive electrode active material due to charge and discharge causes the particles to lose contact with the positive electrode active material. Are dropped to generate a positive electrode active material that is not involved in charge and discharge, and the battery capacity is reduced.

The metal fiber sintered plate of the current collector for the positive electrode has a fiber diameter of 1 to 5 for the same reason as the metal fiber sintered plate of the current collector for the negative electrode.
It is preferably 0 μm, more preferably 5 to 25 μm. The porosity is preferably 50 to 95%. If it is less than 50%, the amounts of the positive electrode active material and the polymer electrolyte that can be filled in the fiber sintered plate decrease, and the capacity of the battery decreases. If it exceeds 95%, the strength of the metal fiber sintered plate becomes weak. Preferred forms of the metal fiber sintered plate of the current collector for the positive electrode are a short fiber sintered body and a long fiber sintered body for the same reason as the metal fiber sintered plate of the negative electrode current collector.

The particle size of the powder of the positive electrode active material to be filled in the current collector made of the above-mentioned foamed metal plate or sintered metal fiber plate is such that the gap between the current collectors can be easily filled and lithium can be smoothly absorbed and released. 1-80μ to be done and not bulky
m is preferable.

The positive electrode active material in the present invention is a material capable of occluding and releasing lithium ions. For example, Ti, Zr, Hf of group 4 of the periodic table, V, Nb, Ta of group 5 and C of group 6
r, Mo, W, Group 7 Mn, Group 8 Fe, Ru, Group 9 Co, Group 10 Ni, Group 11 Cu, Group 12 Zn, C
d, Al, Ga, In of group 13; Sn, Pb of group 14;
Oxides and composite oxides containing a metal such as Sb and Bi of Group 15 and Te of Group 16 as main components, chalcogenides such as sulfides, oxyhalides, and composite oxides of the above metals and lithium can be used. .

As the lithium-containing compound used for the positive electrode active material, a composite oxide of lithium and manganese, a composite oxide of lithium and cobalt, and a composite oxide of lithium and nickel are particularly preferable. The particle size of these lithium-containing oxides is preferably 30 μm or less from the viewpoint of stabilizing the slurry for forming the positive electrode body or developing the strength of the positive electrode layer itself.

Among the above-mentioned lithium-containing composite oxides, the positive electrode active material in which a part of Mn of the spinel-type lithium manganese-based composite oxide represented by the composition formula of LiMn ₂ O ₄ is substituted with another element is activated. High potential and excellent charge / discharge cycle durability. In particular, Li _p Mn _2-xy F _x Z
n _y O ₄ composite oxide represented (0 <p ≦ 1,0 ≦ x <
When 0.4, 0 ≦ y <0.4 and 0 <x + y <0.4) are used, the operating potential is high and the charge / discharge cycle durability is excellent, so that it is preferable. Particularly, those satisfying 0.2 ≦ x ≦ 0.4 and 0.04 ≦ y ≦ 0.15 are preferable.

When the electron conductivity of the positive electrode active material itself is insufficient, a conductive material may be added to the positive electrode active material. As the conductive material, natural graphite having good conductivity or artificial graphite highly graphitized is preferably used. Moreover, in order to improve the absorbency of the electrolyte while maintaining the conductivity, the positive electrode layer 1 to 1
5% by weight of carbon black may be added. The particle size of these conductive materials is preferably 5 μm or less.

Further, a conductive polymer material such as a polyaniline derivative, a polypyrrole derivative, a polythiophene derivative, a polyacene derivative, a polyparaphenylene derivative, or a copolymer thereof may be used in combination.

In the present invention, the non-aqueous electrolyte is a polymer electrolyte obtained by holding a non-aqueous solution containing an electrolyte in a polymer matrix. The polymer matrix is preferably a copolymer containing two or more kinds of polymerized units, and one or more of the polymerized units is preferably a polymerized unit based on a fluoroolefin. It preferably comprises a solvent capable of dissolving the lithium salt. At this time, a battery in which the polymer has high electrochemical stability and can be operated stably at a high voltage is obtained.

Various fluoroolefins can be used as a raw material for obtaining a copolymer containing polymerized units based on a fluoroolefin by polymerization, but the copolymer is excellent in copolymerizability with other monomers and has a high polymer strength. Chlorotrifluoroethylene, tetrafluoroethylene,
Or vinylidene fluoride is preferred. The copolymer of the matrix of the polymer electrolyte in the present invention may be a copolymer obtained by copolymerizing two or more of the above three types of fluoroolefins, but may be one or more of the above three types of fluoroolefins. A copolymer obtained by copolymerizing a monomer with another monomer can be preferably used.

Other monomers copolymerized with the above three kinds of fluoroolefins include, for example, hexafluoroacetone, perfluoro (methyl vinyl ether),
Perfluoro (alkyl vinyl ether) such as perfluoro (propyl vinyl ether), ethylene, propylene, isobutylene, vinyl pivalate, vinyl acetate, vinylene carbonate, ethyl vinyl ether, butyl vinyl ether, cyclohexyl vinyl ether, ethyl allyl ether, cyclohexyl allyl ether, norbornadiene, Crotonic acid esters, alkyl acrylates, alkyl methacrylates, and the like.

Further, along with the above three kinds of fluoroolefins, hexafluoropropylene, trifluoroethylene, vinyl fluoride, (perfluorobutyl) ethylene,
It is also preferable to use a fluoroolefin such as (perfluorooctyl) propylene in combination.

The matrix of the polymer electrolyte is preferably made of chlorotrifluoroethylene, tetrafluoroethylene or fluoride from the viewpoints of electrochemical stability, electric conductivity when the polymer electrolyte is used, adhesion to the current collector, and strength. It is preferable that the copolymer is a copolymer containing a polymerized unit based on at least one member selected from the group consisting of vinylidene and a polymerized unit based on at least one member selected from the group consisting of perfluorovinyl ether, hexafluoropropylene and vinylene carbonate. .

Specifically, vinylidene fluoride / perfluorovinyl ether copolymer, vinylidene fluoride / chlorotrifluoroethylene copolymer, vinylidene fluoride /
Hexafluoropropylene / tetrafluoroethylene copolymer, vinylidene fluoride / hexafluoropropylene copolymer, chlorotrifluoroethylene / vinylene carbonate copolymer and the like are preferable. Particularly, a vinylidene fluoride / perfluorovinyl ether copolymer is preferable because of the excellent properties described above. In this specification, A /
The B copolymer means a copolymer composed of a polymer unit based on A and a polymer unit based on B.

In the present invention, the content of the polymer unit based on fluoroolefin in the copolymer constituting the matrix of the polymer electrolyte is preferably at least 10% by weight. If it is less than 10% by weight, the flexibility of the polymer electrolyte becomes too high, and the strength tends to decrease. In order to obtain a particularly strong polymer electrolyte, the content is preferably 60% by weight or more.

Further, the polymerization unit based on one kind of fluoroolefin is preferably at most 97% by weight,
It is more preferably at most 95% by weight. If the content exceeds 97% by weight, the crystallinity of the polymer is increased, the flexibility is reduced and the moldability is reduced, the solution containing the electrolyte is hardly penetrated into the matrix, and the electric conductivity of the polymer electrolyte is reduced. .

The polymer that forms the matrix of the polymer electrolyte can prevent volume change during charge and discharge of the polymer electrolyte,
From the viewpoint of improving the mechanical strength, it is preferable that crosslinking is performed as necessary. The molecular weight of the polymer forming the matrix of the polymer electrolyte is preferably 10,000 to 1,000,000. When the molecular weight is more than 1,000,000, the dissolution viscosity is extremely high, and it is difficult to uniformly mix the electrolyte solution with the electrolyte solution, and the holding amount of the electrolyte solution is reduced, so that the electric conductivity of the polymer electrolyte is undesirably reduced. If it is less than 10,000, the mechanical strength of the polymer electrolyte is significantly reduced, which is not preferable. Particularly preferably, 30,000 to 500,000 is employed.

The weight ratio of the positive electrode active material / polymer electrolyte in the positive electrode and the weight ratio of the negative electrode active material / polymer electrolyte in the negative electrode are preferably 1/2 to 2/1. If the weight ratio is less than 1/2, the capacity of the battery decreases. If it exceeds 2/1, the bonding strength to the current collector decreases and the bonding strength between the active materials decreases. More preferably, it is 2/3 to 3/2.

In the present invention, the content of the polymerized unit based on fluoroolefin in the polymer, the content of other components, the molecular weight of the polymer, and the like are determined by the solubility or dispersibility of the matrix in an organic solvent for forming a film. It can be appropriately selected depending on the miscibility of the matrix with the electrolyte solution, the retention of the electrolyte solution, the adhesion of the polymer electrolyte to the current collector metal, the strength, the moldability, the handleability, the availability of the matrix, and the like.

The electrolyte solution in the polymer electrolyte secondary battery of the present invention is preferably a solution comprising a lithium salt as a solute and a solvent capable of dissolving the lithium salt. The solvent is preferably a carbonate ester. Carbonate can be used either cyclic or chain. Examples of the cyclic carbonate include propylene carbonate and ethylene carbonate. Examples of the chain carbonate include dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, methyl propyl carbonate, methyl isopropyl carbonate and the like.

In the present invention, the above-mentioned carbonates can be used alone or in combination of two or more. It may be used by mixing with other solvents. Further, depending on the material of the negative electrode active material, the combined use of a chain carbonate and a cyclic carbonate may improve the discharge characteristics, cycle durability, and charge / discharge efficiency.

The lithium salts include ClO ₄ ⁻ , C
F ₃ SO ₃ ⁻ , BF ₄ ⁻ , PF ₆ ⁻ , AsF ₆ ⁻ , SbF ₆ ⁻ , C
It is preferable to use at least one of lithium salts having an anion such as F ₃ CO ₂ ⁻ and (CF ₃ SO ₂ ) ₂ N ⁻ . In the lithium salt solution according to the present invention, it is preferable that the lithium salt is dissolved in the solvent at a concentration of 0.2 to 2.0 mol / L. Outside this range, the ionic conductivity decreases and the electrical conductivity of the polymer electrolyte decreases. More preferably, 0.5 to 1.5 mol / L is selected.

In the present invention, a mixture of a polymer electrolyte and a positive electrode active material in which the lithium salt solution is uniformly distributed in a matrix is used as a positive electrode by integrating it with a positive electrode current collector. Is 30
~ 90% by weight is preferred. If it is less than 30% by weight, the electric conductivity is low. If it exceeds 90% by weight, the polymer electrolyte cannot maintain a solid state. Particularly preferably 40 to 80% by weight
Is adopted.

The layer disposed between the positive electrode body and the negative electrode body in the present invention and having a function as a separator can be formed, for example, as follows. That is, the mixed solution for forming a polymer electrolyte is formed into a slurry, and is coated on a glass plate by a bar coater or a doctor blade, cast or spin-coated, and then dried to remove an organic solvent in which the polymer is mainly dissolved or dispersed. Is peeled off from the glass plate to obtain a film made of a polymer electrolyte, which is used as a separator. If the solvent of the electrolyte solution partially evaporates during drying, the film is newly impregnated with the solvent or the film is exposed to the solvent vapor to obtain a desired composition.

It is preferable to use a porous polypropylene, a porous polytetrafluoroethylene, a nonwoven fabric, a polymer woven fabric, a net, or the like as a reinforcing body and to carry a polymer electrolyte as a separator since the strength can be improved. The polymer matrix of the polymer electrolyte used for the positive electrode, the separator or the negative electrode may have the same composition.
The composition may be varied as necessary in consideration of the reducibility.

In the present invention, when a secondary battery uses a material capable of occluding and releasing lithium as a negative electrode active material, lithium is contained in the negative electrode and / or the positive electrode. Generally, a lithium-containing compound is used at the time of synthesis of the positive electrode active material, and lithium is contained in the solid matrix of the positive electrode active material.
In addition, lithium can be contained in the negative electrode by a chemical or electrochemical method before the battery is assembled, or lithium can be contained by bringing lithium metal into contact with the negative electrode and / or the positive electrode when the battery is assembled. There is no particular limitation on the shape of the polymer electrolyte in the present invention. A sheet shape (a so-called film shape), a folded shape, a rolled bottomed cylindrical shape, a button shape, and the like are selected according to the application.

[0055]

EXAMPLES The present invention will be specifically described below with reference to examples and comparative examples, but the present invention is not limited to these examples.

Example 1 Using a stainless steel autoclave with an internal volume of 1 L and equipped with a stirrer, 540 g of ion-exchanged water was added.
tert-butanol 59.4 g, sec-butanol 0.6 g, C ₈ F ₁₇ CO ₂ NH ₄ 6 g, Na ₂ H
12 g of PO ₄ .12H ₂ O and 6 g of ammonium persulfate
g, FeSO ₄ · 7H ₂ O to 9mg, EDTA · 2H ₂
11 g of O (ethylenediaminetetraacetic acid dihydrate), CF ₂
= CFOCF ₂ CF ₂ CF ₃ was added, and the gas phase was replaced with nitrogen. Then, 99.8 g of vinylidene fluoride was charged.

After the temperature was raised to 25 ° C., CH ₂ OHSO ₂ N
a. A 1% by weight aqueous solution of 2H ₂ O (Rongalit) was added to 21
The polymerization reaction was performed by adding at a rate of mL / hr. Since the pressure decreased with the progress of the reaction, vinylidene fluoride was charged so as to maintain a pressure of 23 atm. After 5 hours, the polymerization was stopped by purging the gas phase to obtain an emulsion having a concentration of 30% by weight.

Agglomeration, washing, drying, vinylidene fluoride /
A CF ₂ = CFOCF ₂ CF ₂ CF ₃ copolymer was recovered. The composition of this copolymer is such that the ratio of polymerization units based on vinylidene fluoride / polymerization units based on CF ₂ = CFOCF ₂ CF ₂ CF ₃ is 89/11 (weight ratio), and the intrinsic viscosity using THF as a solvent is 1 It was 0.4 dL / g.

In an argon atmosphere, 8 g of the copolymer was dissolved in 48 g of THF by heating while stirring. This is designated as solution 1. Next, Li was added to a solvent in which ethylene carbonate and propylene carbonate were mixed at a volume ratio of 1/1.
The PF ₆ dissolved in an argon atmosphere at a concentration of 1 mol / L. This is designated as solution 2.

3 g of solution 2 was added to 21 g of solution 1 and
The mixture was heated to 0 ° C. and stirred. This solution was applied on a glass plate with a bar coater, and dried at 40 ° C. for 1 hour to remove THF to obtain a transparent polymer electrolyte film having a thickness of 100 μm. The composition of this film is as follows: copolymer, ethylene carbonate / propylene carbonate mixed solvent, LiPF
₆ was 50 / 44.3 / 5.7 by weight.

The film was peeled off from the glass substrate, and the electric conductivity was measured by an alternating current impedance method at 25 ° C. in an argon atmosphere to be 3.8 × 10 ⁻⁴ S / cm.
Met.

SUS31 having a diameter of 8 μm and a length of 1 cm or more
0.94m thickness obtained by sintering a mat made of 6L fiber
m, a basis weight of 530 g / m ² and a porosity of 93% were used as the positive electrode current collector. 5.42 g of Li _0.95 Fe _0.25 Zn _0.05 Mn _1.7 O ₄ powder having an average particle size of 5 μm as a positive electrode active material, 0.68 g of graphite powder having a particle size of 1 μm or less as a conductive material, 2.8 g of the above copolymer, and a solution were prepared. 5.4 g of 2 and 20 g of THF were mixed in an argon atmosphere, and heated with stirring to obtain a slurry. This slurry was impregnated into the stainless steel sintered plate, dried and pressed to obtain a positive electrode body having a thickness of 0.4 mm. This cathode body is 18
No abnormalities such as peeling were observed even when bent at 0 °.

Carbon powder (specific surface area: 2.
0 m ² / g, average diameter 10 μm, (002) interplanar spacing 0.
3358nm, crystallite size L _c 80nm) 5.88
g, 2.8 g of the above copolymer, 5.4 g of solution 2, and T
HF (20 g) was mixed in an argon atmosphere and heated with stirring to obtain a slurry. This slurry was obtained by sintering a mat made of SUS316L fiber having a diameter of 20 μm and a length of 1 cm or more, a thickness of 0.55 mm, a basis weight of 450 g / m ² ,
A stainless steel sintered plate having a porosity of 90% was used as a current collector, and a 0.38 mm thick negative electrode was obtained in the same manner as the positive electrode. No abnormality such as peeling was observed even when the negative electrode was bent at 180 degrees.

The above-mentioned polymer electrolyte film was 1.5 cm
Formed into corners, through which the effective electrode area 1 cm x 1 cm
The positive electrode and the negative electrode were opposed to each other, sandwiched and clamped between two 1.5 cm-thick 3 cm square polytetrafluoroethylene back plates, and the outside thereof was covered with an exterior film to assemble a lithium ion secondary battery element. This operation was all performed in an argon atmosphere.

The charge and discharge conditions were a constant current of 2 C, and a charge and discharge cycle test was performed under the potential regulation of a charge voltage up to 4.2 V and a discharge voltage up to 2.5 V. The initial discharge capacity is 6.5
mAH and the capacity retention after 50 cycles was 95%.

[Example 2] 1.52 m thick negative electrode current collector
m, a lithium-ion secondary battery element was assembled in the same manner as in Example 1 except that a foamed nickel plate having a weight of 550 g / m ² , an average opening diameter of 0.4 mm, and a porosity of 96% was used.
A charge / discharge cycle test was performed in the same manner as described above. The initial discharge capacity was 6.9 mAH, and the capacity retention after 50 cycles was 96%. Further, even when the negative electrode body was bent by 180 degrees, no abnormality such as peeling was observed.

[Example 3] Thickness 1.53 mm, weight per unit area 125
A stainless steel sintered plate having 0 g / m ² and a porosity of 90% was used as a positive electrode current collector, filled with a positive electrode active material and a polymer electrolyte,
Example 1 except that the thickness after drying and pressing was 0.64 mm
In the same manner as in the above, a positive electrode body was obtained. In addition, thickness 1.45mm,
A foamed nickel plate having a basis weight of 1290 g / m ² , an average opening diameter of 0.5 mm and a porosity of 90% was used as a negative electrode current collector, filled with a negative electrode active material and a polymer electrolyte, dried, and pressed to a thickness of 0.5 mm. A negative electrode body was obtained in the same manner as in Example 1 except that the above conditions were satisfied. No abnormality such as peeling was observed even when the positive electrode body and the negative electrode body were bent by 180 degrees.

Using the above-mentioned positive electrode body and negative electrode body, a lithium ion secondary battery element was assembled in the same manner as in Example 1, and a charge / discharge cycle test was performed in the same manner as in Example 1. The initial discharge capacity was 9.8 mAH, and the capacity retention rate after 50 cycles was 9
1%.

Example 4 Thickness 3.0 mm, porosity 93%
A foamed aluminum plate having an average pore diameter of 0.4 mm per unit foam is used as a positive electrode current collector, and is filled with a positive electrode active material and a polymer electrolyte,
A lithium ion secondary battery element was assembled in the same manner as in Example 3, except that the thickness after drying and pressing was 1.0 mm to prepare a positive electrode body. The initial discharge capacity was 10.5 mAH. No abnormality such as peeling was observed even when the positive electrode body was bent by 180 degrees.

Example 5 In Example 1, a chlorotrifluoroethylene / vinylene carbonate copolymer (74/26 by weight) was used as a copolymer, and a LiCoO ₂ powder having a particle diameter of 7 μm was used as a positive electrode active material. Example 1 except for
Assemble the lithium ion secondary battery element in the same manner as
A charge / discharge cycle test was performed in the same manner as in Example 1. The initial discharge capacity was 7.3 mAH, and the capacity retention rate after 50 cycles was 92.
%Met. No abnormality such as peeling was observed even when the positive electrode body was bent by 180 degrees.

Example 6 Thickness obtained by sintering a mat made of titanium fiber having a diameter of 35 μm and a length of 1 cm or more was 0.53.
A lithium ion secondary battery element was assembled in the same manner as in Example 1, except that a titanium fiber sintered plate having a thickness of 300 g / m ² and a porosity of 87% was used as the positive electrode current collector. A cycle test was performed. Initial discharge capacity is 5.5mA
H, and the capacity retention after 50 cycles was 90%. No abnormality such as peeling was observed even when the positive electrode body was bent by 180 degrees.

[Example 7] Thickness 30 where only the surface was roughened
When the positive electrode slurry used in Example 1 was coated and dried using an aluminum foil having a thickness of μm as the positive electrode current collector, when the thickness after drying of the coating film was 110 μm or more, the electrode layer was peeled off from the current collector and endured. Did not. Therefore, the thickness after drying the coating is 100μ
m, and a lithium ion secondary battery element was assembled in the same manner as in Example 1 except that this positive electrode body was used, and a charge / discharge cycle test was performed. The initial discharge capacity was 1.8 mAH. The capacity retention after 50 cycles was 75%. When the positive electrode body was bent by 180 degrees, peeling of the electrode layer was observed.

[Example 8] Thickness 20 in which only the surface was roughened
μm copper foil as a negative electrode current collector, the negative electrode slurry used in Example 1 was applied to this foil and dried. When the thickness after coating film drying was 100 μm or more, the electrode layer was peeled off from the current collector, Did not endure use. Therefore, the thickness after coating film drying is 90 μm
Example 1 except that a negative electrode body was prepared
Assemble the lithium ion secondary battery element in the same manner as
A charge / discharge cycle test was performed. Initial discharge capacity is 1.6m
AH, and the capacity retention rate after 50 cycles was 70%. Peeling was observed when the negative electrode body was bent by 180 degrees.

Example 9 (Comparative Example) The same as Example 1 except that the positive electrode body having a dry film thickness of 100 μm prepared in Example 7 and the negative electrode body having a dry film thickness of 90 μm prepared in Example 8 were used. Then, a lithium ion secondary battery element was assembled, and a charge / discharge cycle test was performed. The initial discharge capacity is 1.3 mAH,
The capacity retention after 50 cycles was 35%.

[0075]

According to the polymer electrolyte secondary battery of the present invention, the positive electrode and / or the negative electrode have a strong binding force between the active material and the polymer electrolyte and the current collector, and thus have excellent charge / discharge cycle characteristics.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Hiroki Kamiya 1150 Hazawa-cho, Kanagawa-ku, Yokohama-shi, Kanagawa Prefecture Inside the Asahi Glass Co., Ltd. (72) Inventor Masayuki Tamura 1150 Hazawa-cho, Kanagawa-ku, Yokohama-shi, Kanagawa Asahi Glass Co., Ltd. Central Research Laboratory

Claims (5)

[Claims] A positive electrode body and a negative electrode body comprising a metal current collector and an electrode layer containing a non-aqueous solution containing an active material and an electrolyte and a polymer holding the solution are integrated with each other. In a polymer electrolyte secondary battery having a polymer electrolyte in which a non-aqueous solution containing an electrolyte is interposed between the anode bodies and held in a polymer matrix, the cathode body and / or the anode body may have a metal current collector. A polymer electrolyte secondary battery, which is a foamed metal plate or a sintered metal fiber plate made of a metal that does not form an alloy with lithium, wherein an electrode layer is filled in a metal current collector. 2. The metal current collector for a negative electrode comprises a foamed metal plate containing nickel as a main component, a fiber sintered plate or a stainless steel sintered plate containing nickel as a main component, and the thickness of the negative electrode body is reduced. The polymer electrolyte secondary battery according to claim 1, which has a thickness of 0.2 to 2 mm. 3. The metal current collector for a positive electrode is a foamed aluminum plate, an aluminum metal fiber sintered plate, a titanium fiber sintered plate or a stainless steel sintered plate, and the thickness of the positive electrode body is 0.2 to 0.2 mm. The polymer electrolyte secondary battery according to claim 1, wherein the size is 2 mm. 4. A lithium salt comprising a copolymer comprising a polymer electrolyte comprising two or more polymerized units, wherein at least one of the polymerized units is a polymer unit based on a fluoroolefin. The polymer electrolyte secondary battery according to claim 1, 2 or 3, which is a polymer electrolyte containing a solution comprising a solute and a solvent capable of dissolving a lithium salt. 5. A polymer electrolyte matrix comprising a polymerized unit based on at least one selected from the group consisting of chlorotrifluoroethylene, tetrafluoroethylene and vinylidene fluoride, and perfluorovinyl ether, hexafluoropropylene and vinylene carbonate. The polymer electrolyte secondary battery according to claim 4, which is a copolymer containing a polymerized unit based on at least one selected from the group.